[PATCH v2] ipc: Update semtimedop() to use hrtimer

[PATCH v2] ipc: Update semtimedop() to use hrtimer

[Prakash Sangappa]

semtimedop() should be converted to use hrtimer like it has been done
for most of the system calls with timeouts. This system call already
takes a struct timespec as an argument and can therefore provide finer
granularity timed wait.

v1->v2:
  - Use timespec64_valid() to validate timeout
     and other changes as suggested by Thomas Gleixner

Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
---
 ipc/sem.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 0dbdb98..44b65b6 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1995,7 +1995,9 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 	int max, locknum;
 	bool undos = false, alter = false, dupsop = false;
 	struct sem_queue queue;
-	unsigned long dup = 0, jiffies_left = 0;
+	unsigned long dup = 0;
+	ktime_t expires, *exp = NULL;
+	bool timed_out = false;
 
 	if (nsops < 1 || semid < 0)
 		return -EINVAL;
@@ -2003,12 +2005,11 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		return -E2BIG;
 
 	if (timeout) {
-		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
-			timeout->tv_nsec >= 1000000000L) {
-			error = -EINVAL;
-			goto out;
-		}
-		jiffies_left = timespec64_to_jiffies(timeout);
+		if (!timespec64_valid(timeout))
+			return -EINVAL;
+		expires = ktime_add_safe(ktime_get(),
+				timespec64_to_ktime(*timeout));
+		exp = &expires;
 	}
 
 
@@ -2166,10 +2167,8 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		sem_unlock(sma, locknum);
 		rcu_read_unlock();
 
-		if (timeout)
-			jiffies_left = schedule_timeout(jiffies_left);
-		else
-			schedule();
+		timed_out = !schedule_hrtimeout_range(exp,
+				current->timer_slack_ns, HRTIMER_MODE_ABS);
 
 		/*
 		 * fastpath: the semop has completed, either successfully or
@@ -2210,7 +2209,7 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		/*
 		 * If an interrupt occurred we have to clean up the queue.
 		 */
-		if (timeout && jiffies_left == 0)
+		if (timed_out)
 			error = -EAGAIN;
 	} while (error == -EINTR && !signal_pending(current)); /* spurious */
 
-- 
2.7.4

Re: [PATCH v2] ipc: Update semtimedop() to use hrtimer

[Thomas Gleixner]

Prakash,

On Thu, Apr 28 2022 at 08:07, Prakash Sangappa wrote:
> semtimedop() should be converted to use hrtimer like it has been done
> for most of the system calls with timeouts. This system call already
> takes a struct timespec as an argument and can therefore provide finer
> granularity timed wait.

almost perfect :)

The v1->v2: description wants to be below the '---' separator. It's not
part of the changelog and just helpful for reviewers to assess the
history of the patch(set).

> v1->v2:
>   - Use timespec64_valid() to validate timeout
>      and other changes as suggested by Thomas Gleixner
>
> Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
> ---
...
> @@ -2210,7 +2209,7 @@ long __do_semtimedop(int semid, struct sembuf *sops,
>  		/*
>  		 * If an interrupt occurred we have to clean up the queue.
>  		 */
> -		if (timeout && jiffies_left == 0)
> +		if (timed_out)
>  			error = -EAGAIN;
>  	} while (error == -EINTR && !signal_pending(current)); /* spurious */

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>